JP3827149B2 - Titanium alloy member and manufacturing method thereof - Google Patents

Description

  The present invention relates to a titanium alloy member excellent in cold workability that can be used for various products in various fields. The present invention also relates to a manufacturing method that can efficiently manufacture the titanium alloy member.

  Titanium alloys have been used in the fields of aviation, military, marine, space, etc. because they are lightweight and have high strength (because of high specific strength). However, since titanium alloys usually have poor workability and formability, the material yield is poor, and titanium products are generally expensive. Therefore, the range of use has also been limited.

  Recently, titanium alloys having relatively excellent workability (for example, Ti-22V-4Al: trade name DAT51 etc.) have been developed, and titanium products have been increasing around us. However, the processability is still not sufficient, and as the processing rate increases, the ductility often decreases rapidly. Therefore, if a titanium alloy having excellent workability is obtained, the material yield of titanium products can be improved, and the production volume can be increased and further applications can be expanded.

  In addition to such workability, a titanium alloy having a low Young's modulus and a high strength has been demanded in order to expand the application of titanium products. If such a titanium alloy is obtained, the degree of freedom of design of various products increases dramatically as it is difficult to achieve with conventional materials. For example, when a titanium alloy having a low Young's modulus and a high strength is used for a golf club head, the natural frequency of the face portion can be reduced, and the natural frequency of the face portion can be tuned to the natural frequency of the golf ball. Thereby, it is said that a titanium golf club capable of remarkably extending the flight distance of the golf ball can be obtained. In addition, for example, when a high strength titanium alloy with a low Young's modulus is used for the spectacle frame (particularly the vine portion), an excellent fit can be obtained, and its functionality is great in combination with lightness and allergy resistance. It is said to improve.

  As described above, if a titanium alloy having excellent workability, low Young's modulus and high strength is developed, it is considered that the demand for titanium alloy members (titanium products) using the titanium alloy will further increase.

  The present invention has been made in view of such circumstances, and provides a titanium alloy member having excellent workability, low Young's modulus, and high strength that could not be achieved by conventional titanium alloys. Objective.

As a result of intensive studies to solve this problem and various systematic experiments, the present inventor discovered a completely new titanium alloy that could satisfy these requirements and completed the present invention.
(Titanium alloy member)
(1) Titanium alloy member viewed from the texture The inventor first discovered that the titanium alloy has a special structure, and has developed the titanium alloy member of the present invention.

That is, the titanium alloy member of the present invention comprises 40% by mass or more of titanium (Ti), a total of 90% by mass or more of the titanium and other IVa group elements and Va group elements, and oxygen (O ), Nitrogen (N), and carbon (C), and a total of one or more elements in the interstitial element group comprising 0.6 to 2.0% by mass,
a ratio of the interatomic distance on the c axis to the interatomic distance on the a axis (c / a) is a body-centered tetragonal or body-centered cubic crystal grain having a ratio of 0.9 to 1.1,
The pole figure of the (110) or (101) crystal plane of the crystal grain is parallel to the plane including the machining direction in the range of 20 ° <α ′ <90 ° and 0 ° <β <360 ° by the Schlutz reflection method. When the measured values (X) that are measured and evenly distributed on the pole figure are statistically processed, the second moment (ν2) around the average value (Xm) defined by the following equation is the square of the average value (Xm ² ) divided by (ν2 / Xm ² ) is 0.3 or more, and the third moment (ν3) around the mean value (Xm) defined by the following equation is divided by the cube of the mean value (Xm ³ ) The value (ν3 / Xm ³ ) is 0.3 or more, and 1.6 times the average value (1 in the measurement values measured in the range of 55 ° <α ′ <65 ° and β along the machining direction (1 .6Xm) a titanium alloy member characterized by having a texture including a measured value of not less than 6.Xm).

Second moment: ν2 = {Σ (X−Xm) ² } / N
Third moment: ν3 = {Σ (X−Xm) ³ } / N
(However, N is the number of samplings.)
This titanium alloy member contains titanium and IVa group elements and / or Va group elements in terms of composition, is substantially body-centered cubic in terms of crystal structure, and conventional β titanium in terms of organization. It has a special texture that cannot be obtained with alloys.

  The present inventor has found that such a titanium alloy member is excellent in workability, particularly cold workability, and has a characteristic of low strength and high strength.

  At present, when the titanium alloy member has such a structure or the like, it is not always clear why the cold workability is improved or the strength is increased at a low Young's modulus.

  By the way, the “titanium alloy member” in this specification includes both a titanium alloy and a processed material obtained by subjecting the titanium alloy to some kind of processing. The form of the processed material may be a material such as a plate material or a wire material, an intermediate material or an intermediate product obtained by processing the raw material, or a final product obtained by processing the intermediate material. However, the degree of processing does not matter. This processing includes hot processing as well as cold processing.

Regarding the composition of the above-described titanium alloy member, the reason why titanium is 40% by mass or more and the total of titanium, the IVa group element and the Va group element is 90% by mass or more is that it has excellent cold workability and low Young's modulus. To achieve at the same time.

More preferably, the titanium content is 45% by mass or more, and the total of titanium, the IVa group element and the Va group element is 95% by mass or more.

The IVa group element and the Va group element are not particularly limited as long as they are those group elements. The IVa group elements include zirconium (Zr) and hafnium (Hf), and the Va group elements include niobium (Nb), tantalum (Ta), and vanadium (V). It is preferable to select appropriately from the viewpoint of specific gravity and raw material cost.

Although the crystal structure is a body-centered tetragonal or body-centered cubic crystal having a c / a of 0.9 to 1.1, it is not always necessary to strictly distinguish between the two. It is sufficient if it has a structure that is considered to be almost body-centered cubic.
(2) Titanium alloy member viewed from specific composition Next, the present inventor is that the titanium alloy member having the above-described excellent workability, low Young's modulus and high strength has a specific composition satisfying specific parameters. As a result, the present invention was completed.

  That is, in the titanium alloy member of the present invention, the compositional average value of the substitutional element is 2.43 <Md <2.49 with respect to the energy level Md of the d electron orbit, which is a parameter obtained by the DV-Xα cluster method, and the bond order Bo. It is characterized by comprising titanium and an alloy element having a specific composition in which the compositional average value of the substitutional element is 2.86 <Bo <2.90.

At present, the detailed expression mechanism is not clear, but the titanium alloy member has a specific composition within a limited range of 2.43 <Md <2.49 and 2.86 <Bo <2.90. It was found that the above-described excellent characteristics were exhibited.
(3) Titanium alloy member from the viewpoint of dislocation density Further, the present inventor has found that the above-described excellent workability, low Young's modulus, or high strength titanium alloy member (especially cold worked member) is almost dislocated inside the crystal. It was discovered that it does not have (linear lattice defects), and the present invention has been completed.

That is, the titanium alloy member of the present invention is characterized in that the dislocation density inside the crystal grains is 10 ¹¹ / cm ² or less when cold-working 50% or more.

  Traditionally, plastic deformation of metals has been described as slip deformation or twin deformation. In particular, in a conventional β-titanium alloy, plastic deformation due to slip deformation is dominant, and this slip deformation has been explained by the movement of the dislocation. In general, the dislocation increases as the cold working rate increases to cause work hardening. For this reason, when a conventional titanium alloy material is subjected to cold working with a high working rate without performing intermediate annealing or the like, cracks and the like often occur.

  However, in the case of the titanium alloy member of the present invention, cold working can be repeated even when heat treatment or the like is not performed, and cracks and the like do not occur even when the cold working rate increases. At present, the reason for this is not clear, but it can be considered that plastic deformation is caused by a mechanism different from that of the conventional metal material based on the dislocation density.

In any case, since the titanium alloy member of the present invention is remarkably excellent in cold workability, it is effective in improving the (material) yield and productivity of the titanium alloy member, and can be used for various products. The degree of freedom can be expanded.
(4) Manufacturing Method of Titanium Alloy Member The inventor has also developed a manufacturing method capable of efficiently manufacturing the titanium alloy member together with the above-described titanium alloy member.

  That is, in the manufacturing method of the titanium alloy member of the present invention, the compositional average value of the substitutional element is 2.43 <Md <2.49 with respect to the energy level Md of the d electron orbit, which is a parameter obtained by the DV-Xα cluster method. A preparation step for preparing a raw material made of titanium and an alloy element having a specific composition in which the compositional average value of substitutional elements with respect to the order Bo is 2.86 <Bo <2.90, and titanium made of the raw material after the preparation step A member forming step of forming an alloy member.

  According to the preparation process of the present invention, the composition of the titanium alloy member that exhibits the above-described excellent workability, high strength, or low Young's modulus can be easily specified, and the titanium alloy member is reliably and efficiently manufactured.

  The “high strength” in the present specification means that the tensile strength or the tensile elastic limit strength described later is large. In addition, “low Young's modulus” means that the average Young's modulus described later is smaller than the Young's modulus of a conventional metal material.

FIG. 1 is a schematic diagram showing an outline of a pole figure measurement method by a Schlutz reflection method.
2 shows a sample No. 1 according to the example. It is a figure which shows the X-ray-diffraction result of 2.
3 shows a sample No. 1 according to the example. 1 is a pole figure of 1. FIG.
4 shows a sample No. 1 according to the example. 4 is a pole figure of FIG.
5 shows a sample No. 1 according to the example. 5 is a pole figure of FIG.
6 shows a sample No. according to the example. FIG.
7 shows a sample No. according to the example. FIG.
FIG. 8 is a pole figure of a comparative sample.
FIG. 9 is an explanatory diagram relating to the definition of the weight function W.
10 shows a sample No. 1 according to the example. 1 is a TEM (bright field image) photograph showing a metal structure of 1;
11 shows a sample No. according to the example. It is a TEM (bright field image) photograph which shows 1 'metal structure.
12 shows a sample No. 1 according to the example. 1 is a TEM (dark field image: −16.3 °) photograph showing a metal structure of 1;
13 shows a sample No. according to the example. 1 is a TEM (dark field image: 6.1 °) photograph showing a metal structure of 1;
FIG. 14A is a diagram schematically showing a stress-strain diagram of a titanium alloy member according to the present invention.
FIG. 14B is a diagram schematically showing a stress-strain diagram of a conventional titanium alloy.

A. Embodiments The titanium alloy member of the present invention will be described in detail below with reference to embodiments.

The titanium alloy member having the texture described above, a titanium alloy member having a dislocation density, a titanium alloy member having a composition characterized by the energy level of d-electron orbitals and the bond order, and a method for manufacturing the titanium alloy member These components can be selectively combined with each titanium alloy member or its manufacturing method as appropriate. In addition, it should be noted that each of the limiting elements described later can be selectively combined as appropriate with respect to each component of the titanium alloy member or the manufacturing method thereof.
(1) Texture The texture is a deformed texture in which each crystal has a preferred orientation, which is formed when (strong) processing is performed on a polycrystal. In addition to the processed texture, the texture includes a recrystallized texture formed when the processed texture is recrystallized.

  The texture is measured by various methods. Here, the state of the texture is clarified from a pole figure obtained by stereo projection using a general Schlutz reflection method. An outline of a pole figure measurement method by the Schlutz reflection method is shown in FIG.

In addition, each measured value on the pole figure is statistically processed, and the second or third moment (ν2, ν3) around the average value (Xm) is expressed by the square or the third power of the average value (Xm ² , Xm ³ ), respectively. The reason why the divided values (ν2 / Xm ² , ν3 / Xm ³ ) are used is to facilitate objective comparison with other materials.

Here, ν2 / Xm ² indicates the bias of the measured value. When ν2 / Xm ² is less than 0.3, it means that the deviation of the (110) plane or the (101) plane in the pole figure is not large, and the elastic anisotropy is not sufficient, which is not preferable.

Further, .nu.3 / Xm ^3, if it is large in the range of positive numbers indicate that the measured values are projected at a greater area than the average value (Xm). If .nu.3 / Xm ³ is less than 0.3, means that the concentration in a particular part of the (110) plane or (101) plane in the diagram pole not large, the elastic anisotropy of the material is sufficient Not preferred.

On the other hand, if ν2 / Xm ² is 0.3 or more and ν3 / Xm ³ is 0.3 or more, the deviation of the (110) plane or the (101) plane is sufficiently large and the concentration in a specific portion is sufficient. And is considered to be a preferable material having sufficiently large elastic anisotropy. More preferably, ν2 / Xm ² is 0.4 or more, 0.5 or more, or 0.6 or more, and ν3 / Xm ³ is 0.4 or more, 0.5 or more, or 0.6 or more.

  The titanium alloy member of the present invention is characterized in that the portion where the (110) plane or (101) plane is concentrated is limited to a part on the pole figure, and this is the elastic anisotropy of the titanium alloy member. It can be thought of as reflecting the “anisotropic” characteristics of.

In particular, if “measured value of 1.6 times (1.6 × m) or more of the average value is included in the measured value measured in the range of 55 ° <α ′ <65 ° and β along the machining direction”, It can be determined that the member has material characteristics having favorable anisotropy. It is more desirable to have a measured value that is at least 1.8 times the average value, and more preferably at least 2.5 times the average value.

If the titanium alloy member has a cold-worked structure of 50% or more in which the dislocation density inside the crystal grains is 10 ¹¹ / cm ² or less in addition to such a texture, the Young's modulus is further reduced. Is preferred.
(2) Composition
<1> The titanium alloy member of the present invention has a total of one or more elements in an interstitial element group consisting of interstitial elements, for example, oxygen (O), nitrogen (N), and carbon (C). Containing 25 to 2.0 mass% is preferable. And it is more preferable when the sum total is 0.3-1.8 mass % and 0.6-1.5 mass %. In particular, it is more preferable that the total exceeds 0.6 mass % and is 2.0 mass % or less, 1.8 mass % or less, or 1.5 mass % or less.

  Oxygen, nitrogen, and carbon are interstitial solid solution elements, and it is generally said that high strength titanium alloys can be obtained by solid solution strengthening. On the other hand, it has been known that the titanium alloy becomes brittle when the solid solution amount of these elements increases. Therefore, in the case of a conventional titanium alloy, the oxygen content and the like can be allowed only up to about 0.25% by mass. Moreover, in the case of a titanium alloy, special care is taken to control the oxygen amount within the range, which has been a major factor in raising the manufacturing cost.

  However, the present inventor overturns such common sense that the titanium alloy according to the present invention exhibits extremely toughness and high elastic deformability even if it contains a large amount of O, N, or C, which has never existed before. discovered. This discovery is groundbreaking in the titanium alloy industry and is very significant academically. The detailed reason is not clear, but we are currently eagerly studying it. In the case of the titanium alloy member of the present invention, since the characteristics are improved by containing a large amount of oxygen, nitrogen or carbon, it is no longer necessary to strictly control the oxygen amount. Therefore, the characteristics of such a titanium alloy member are also preferable for improving the productivity and economy.

  Needless to say, if the amount of oxygen, nitrogen, or carbon is too small, sufficient strength cannot be achieved. On the other hand, if the amount of these elements is too large, the toughness and ductility of the titanium alloy member are lowered, which is not preferable.

In addition, although the composition range of each element was shown in the form of “x to y mass %”, this includes the lower limit (x) and the upper limit (y) unless otherwise specified.
(3) Energy level and bond order of d-electron orbital The energy level and bond order of d-electron orbital are parameters specific to substitutional (alloy) elements determined by the DV-Xα cluster method.

  The DV-Xα cluster method is a kind of molecular orbital method that can skillfully simulate the local electronic state around an alloy element (Reference: Introduction to Quantum Material Chemistry, Hirohiko Adachi, Sankyo Publishing) (1991)).

  Specifically, a model is created using clusters (virtual molecules in the crystal) corresponding to each crystal lattice, and the central substitutional alloy element M is changed, and M and the master alloy X (in this case, X is The state of chemical bonding with Ti is examined. The DV-Xα cluster method is a method for obtaining an alloy parameter representing the individuality indicated by M as an alloy component in the mother alloy. If it is limited to materials mainly composed of transition metals, it is said that the two parameters of the energy level Md (composition average value) of d electron orbit and the bond order Bo (composition average value) are practically effective. Yes.

  The energy level Md of the d electron orbit indicates the energy level of the d orbital of the substitutional alloy element M and is a parameter correlated with the electronegativity and atomic radius of the atom. The bond order Bo is a parameter representing the degree of electron cloud overlap between the mother alloy element X and the substitutional alloy element M.

  As described above, although the detailed reason is not clear, when the titanium alloy member of the present invention is composed of a plurality of elements satisfying 2.43 <Md <2.49 and 2.86 <Bo <2.90. The above-described excellent characteristics were obtained.

  Then, 2.45 <Md <2.48, 2.46 <Md <2.47, 2.865 <Bo <2.885, and 2.87 <Bo <2.88, More preferred.

In addition, as a specific composition satisfying these parameters, for example, a Va group element is 20 to 50.
A titanium alloy containing mass% and the balance being titanium is conceivable. However, since the range of the parameter is narrow, it should be noted that not all titanium alloys included in the composition range satisfy the parameter.

Also, when looking at this parameter in relation to the above-mentioned texture, when the Md value is 2.49 or more or the Bo value is 2.86 or less, the body-centered cubic (bcc) or body-centered tetragonal (bct) is not. It becomes stable. And since a part of structure | tissue changes to a dense hexagonal crystal (hcp), cold workability falls. On the other hand, when the Md value is 2.43 or less or the Bo value is 2.90 or more, the interatomic bonding force increases, which causes a decrease in cold workability and an increase in Young's modulus.
(4) Cold working and dislocation density
<1> “Cold” means below the recrystallization temperature of the titanium alloy (the lowest temperature at which recrystallization occurs). For example, 50% or more cold work refers to a case where the cold work rate defined by the following equation is 50% or more.

Cold working rate = (S ₀ -S) / S ₀ × 100 (%)
(S ₀ : cross-sectional area before cold working, S: cross-sectional area after cold working)
In addition, the structure | tissue obtained when a titanium alloy (material) is cold worked is called a cold work structure | tissue in this specification.
<2> The dislocation density is the number of dislocations per unit area, and can be obtained, for example, by observing an internal deformed structure using an electron beam or X-ray diffraction phenomenon.

  As described above, the titanium alloy member of the present invention is plastically deformed by an unknown mechanism that is different from conventional metal materials because the dislocation density is so low that it is difficult to observe by ordinary methods even if cold working is performed. It is thought that has occurred. As a result, it is possible to perform processing to a remarkable range (cold) without causing processing cracks and the like. And even if it has a shape that is difficult to form conventionally, according to the titanium alloy member of the present invention, it is considered that plastic working can be performed with a good yield in the cold.

Although the case where 50% or more of cold work was performed was taken up and demonstrated previously, the degree of cold work may be 70% or more, Furthermore, 90% or more, 99% or more may be sufficient. The dislocation density can be 10 ⁷ / cm ² or less.
(5) Manufacturing method
<1> As described above, the manufacturing method of the present invention includes a preparation step and a member formation step.

  The preparation step is a step of preparing a raw material by selecting and determining the type of composition element and the amount of each element so as to satisfy the parameters Md and Bo described above.

  However, the raw material composition in this preparation process does not necessarily completely match the elemental composition of the final titanium alloy member. This is because there may be alloy elements that are mixed in or dropped out in the subsequent member forming step or the like. Therefore, in this case, the raw material is preferably prepared so that the elemental composition of the final titanium alloy member satisfies the aforementioned 2.43 <Md <2.49 and 2.86 <Bo <2.90. Examples of the substitutional alloy element include niobium, tantalum, vanadium, zirconium, hafnium, and the like, and it is preferable that the raw material contains at least one of these elements.

  The member forming step may be a melting method in which the raw material is melted and then the member is formed, or a sintering method in which the raw material powder is sintered.

  For example, in the case of the melting method, the member forming step is a melting step for manufacturing a melting material from the raw material after the preparation step. This melting process can be realized by casting a titanium alloy melted by arc melting, plasma melting, induction skull, or the like (melting process) into a mold or the like (casting process).

  Further, in the case of a sintering method, the preparation step is a powder preparation step for preparing a raw material powder having the specific composition, and the member forming step uses a sintered material from the raw material powder after the powder preparation step. It becomes a sintering process to manufacture.

  The raw material powder used in the powder preparation step may be a mixed powder composed of titanium powder, alloy element powder or alloy powder, or may be composed of a kind of alloy powder having the specific composition (or a composition close to the specific composition). .

  In the sintering step, for example, the mixed powder is filled in a molding die (filling step), the mixed powder is pressure-molded to form a molded body (molding process), and the molded body is heated and sintered ( Heating step). The forming step can also be performed using CIP (cold isostatic pressing). Moreover, you may perform a shaping | molding process and a heating process by HIP (hot isostatic pressing).

In addition, when dissolving titanium, a special apparatus is required and it is necessary to perform multiple dissolution. It is difficult to control the composition during dissolution, especially when a large amount of Va group elements are contained.
Macro component segregation is likely to occur during casting. Therefore, in order to efficiently produce a stable quality titanium alloy member, it is considered that the sintering method is more preferable at present. However, even with the melting method, for example, a titanium alloy member with sufficient quality can be produced by using the method described in the examples described later.

Further, when the sintering method is used, a dense titanium alloy member can be obtained, and a net shape can be obtained even if the product shape is complicated.
<2> When the above-described sintered material or melted material is subjected to the above-described cold working, the titanium alloy member can be further strengthened and have a low Young's modulus.

  Therefore, it is preferable that the manufacturing method of the present invention further includes a cold working step of cold working the sintered material or the melted material.

  Further, a hot working step may be added as appropriate. In particular, in the case of a sintered material, the structure can be densified by hot working. This hot working step is preferably performed after the heat sintering step and before the cold working step.

When the cold working process and the hot working process are performed in accordance with a desired shape of the titanium alloy member, productivity is further improved. In addition, you may consider including the cold work process and the hot work process in the member formation process said by this invention.
<3> Further, the present inventor has found that a high-strength titanium alloy member having excellent high elastic deformability, high tensile elastic limit strength, etc. described later can be obtained by performing an aging treatment step after the cold working step. It was.

  However, before the aging treatment, a solution treatment at a recrystallization temperature or higher may be performed, but since the influence of work strain applied in the titanium alloy by the cold work is lost, the cold work process Higher characteristics can be obtained by directly performing the aging treatment step later.

  The aging treatment conditions include (a) low temperature short time aging treatment (150 to 300 ° C.), (b) high temperature long time aging treatment (300 to 600 ° C.) and the like.

  According to the former, the average Young's modulus can be maintained or lowered while improving the tensile elastic limit strength, and a titanium alloy having high elastic deformability can be obtained. According to the latter, the average Young's modulus slightly increases as the tensile elastic limit strength increases, but the average Young's modulus is still 95 GPa or less. That is, even in this case, the level of increase in average Young's modulus is very low, and a titanium alloy having high elastic deformability and high tensile elastic limit strength can be obtained.

  Furthermore, the present inventor repeats an enormous number of tests, so that the aging treatment step is within the treatment temperature range of 150 to 600 ° C., and the treatment temperature (T ° C.) and treatment time (t hours) based on the following formula: ) And the parameter (P) determined from the above is found to be preferable when the process is 8.0 to 18.5.

P = (T + 273) · (20 + log ₁₀ t) / 1000
The parameter P is a Larson-Miller parameter, which is determined by a combination of the heat treatment temperature and the heat treatment time, and indicates the condition of the aging treatment step (heat treatment).

  When the parameter P is less than 8.0, preferable material properties cannot be obtained even when aging treatment is performed. When the parameter P exceeds 18.5, the tensile elastic limit strength is decreased, the average Young's modulus is increased, or the elastic deformation is performed. It is not preferable because the performance is lowered.

  In addition, it is more suitable that the cold working process performed before this aging treatment process is what makes a cold work rate 10% or more.

  Then, according to the desired characteristics of the titanium alloy member, the aging treatment step is a step in which the parameter P is 8.0 to 12.0 in the treatment temperature range of 150 ° C. to 300 ° C. The titanium alloy member obtained after the process may have a tensile elastic limit strength of 1000 MPa or more, an elastic deformability of 2.0% or more, and an average Young's modulus of 75 GPa or less.

  Similarly, the aging treatment step is a step in which the parameter P is 12.0 to 14.5 when the treatment temperature is in the range of 300 ° C. to 500 ° C., and the titanium alloy member obtained after the aging treatment step is pulled. The elastic limit strength may be 1400 MPa or more, the elastic deformability may be 1.6% or more, and the average Young's modulus may be 95 GPa or less.

In the present specification, unless otherwise specified, the numerical range “x to y” includes the lower limit value x and the upper limit value y.
(5) Tensile elastic limit strength, elastic deformability and average Young's modulus The tensile elastic limit strength is defined as the stress applied when the permanent elongation (strain) reached 0.2% in the tensile test. The elastic deformability is the amount of deformation of the test piece at the tensile elastic limit strength. The average Young's modulus does not indicate an “average” of Young's modulus in a strict sense, but means a Young's modulus that represents the titanium alloy member of the present invention. Specifically, in the stress-strain diagram obtained in the tensile test, the curve slope (tangential slope) at the stress position corresponding to ½ of the tensile elastic limit strength.

  Incidentally, the tensile strength is a stress obtained by dividing the load immediately before the final fracture of the test piece by the cross-sectional area before the test in the parallel portion of the test piece in the tensile test.

  Hereinafter, the tensile elastic limit strength and the average Young's modulus related to the titanium alloy member of the present invention will be described in detail with reference to FIGS. 14A and 14B.

FIG. 14A is a diagram schematically showing a stress-strain diagram of a titanium alloy member according to the present invention, and FIG. 14B is a stress-strain diagram of a conventional titanium alloy (Ti-6Al-4V alloy). It is the figure shown typically.
<1> As shown in FIG. 14B, in the conventional metal material, first, the elongation increases linearly in proportion to the increase in tensile stress (between <1> ′ and <1>). And the Young's modulus of the conventional metal material is calculated | required by the inclination of the straight line. In other words, the Young's modulus is a value obtained by dividing the tensile stress (nominal stress) by the strain (nominal strain) proportional to the tensile stress.

  Thus, in the linear region (between <1> '-<1>) where stress and strain are in a proportional relationship, the deformation is elastic. For example, if the stress is unloaded, the elongation that is the deformation of the test piece Returns to 0. However, when a tensile stress is further applied beyond the linear region, the conventional metal material starts plastic deformation, and even when the stress is unloaded, the elongation of the test piece does not return to 0 and a permanent elongation occurs.

  Usually, the stress σp at which the permanent elongation is 0.2% is referred to as 0.2% proof stress (JIS Z 2241). This 0.2% proof stress was translated by 0.2% elongation (strain) on the straight line (<1> '-<1>: tangent of the rising portion) of the elastic deformation region on the stress-strain diagram. It is also the stress at the intersection (position <2>) between the straight line (<2> '-<2>) and the stress-strain curve.

In the case of a conventional metal material, it is generally considered that 0.2% proof stress≈tensile elastic limit strength based on an empirical rule that “when elongation exceeds about 0.2%, permanent elongation occurs”. Conversely, within this 0.2% proof stress, the relationship between stress and strain is considered to be generally linear or elastic.
<2> However, as can be seen from the stress-strain diagram of FIG. 14A, such a conventional concept does not apply to the titanium alloy member of the present invention. The reason is not clear, but in the case of the titanium alloy member of the present invention, the stress-strain diagram does not become a straight line in the elastic deformation region, but becomes a convex curve (<1>'-<2>). When loaded, the elongation returns to 0 along the same curve <1>-<1>', or the permanent elongation occurs along <2>-<2>'.

  Thus, in the titanium alloy member of the present invention, even in the elastic deformation range (<1> '-<1>), the stress and strain are not in a linear relationship (that is, non-linear), and the stress increases. If it does, distortion will increase rapidly. The same applies to the case of unloading, where the stress and strain are not in a linear relationship, and if the stress decreases, the strain rapidly decreases. Such characteristics are considered to be manifested as the high elastic deformability of the titanium alloy member of the present invention.

  By the way, in the case of the titanium alloy member of the present invention, as can be seen from FIG. 14A, the tangential slope on the stress-strain diagram decreases as the stress increases. Thus, since stress and strain do not change linearly in the elastic deformation region, it is not appropriate to define the Young's modulus of the titanium alloy member of the present invention by the conventional method.

  Further, in the case of the titanium alloy member of the present invention, since stress and strain do not change directly, it is also appropriate to evaluate as 0.2% proof stress (σp ′) ≈tensile elastic limit strength by the same method as before. Absent. That is, the 0.2% proof stress obtained by the conventional method is a value significantly smaller than the original tensile elastic limit strength. Therefore, in the case of the titanium alloy member of the present invention, it cannot be considered that the conventional 0.2% proof stress≈tensile elastic limit strength.

  Therefore, returning to the original definition, the tensile elastic limit strength (σe) of the titanium alloy member of the present invention was determined as described above (position <2> in FIG. 14A). Further, the introduction of the above-mentioned average Young's modulus was considered as the Young's modulus of the titanium alloy member of the present invention.

14A and 14B, σt is the tensile strength, εe is the strain in the tensile elastic limit strength (σe) of the titanium alloy member according to the present invention, and εp is the 0.2% yield strength of the conventional metal material. It is a distortion at (σp).
<3> As described above, it is not clear as to why the titanium alloy member of the present invention exhibits such unique and excellent characteristics. However, from the hard research by the present inventors, it can be considered as follows.

  The inventor investigated a sample of a titanium alloy member according to the present invention. As a result, the titanium alloy member according to the present invention has a structure in which dislocations are hardly introduced and the (110) plane is very strongly oriented in some directions, as described above, even when cold working is performed. It became clear that it was presenting. Moreover, in the dark field image using 111 diffraction spots observed with a TEM (transmission electron microscope), it was observed that the contrast of the image moved with the inclination of the sample. This suggests that the (111) plane being observed is greatly curved, which was also confirmed by direct observation of a high-magnification lattice image. In addition, the radius of curvature of the curvature of the (111) plane was as small as about 500 to 600 nm. This means that the titanium alloy member of the present invention has a property that is not known at all in conventional metal materials, which means that the influence of processing is mitigated not by the introduction of dislocations but by the curvature of the crystal plane. .

In addition, dislocations were observed in a very small part in a state where 110 diffraction spots were strongly excited, but were hardly observed when excitation at 110 diffraction spots was eliminated. This indicates that the displacement component around the dislocation is remarkably biased in the <110> direction, suggesting that the titanium alloy member of the present invention has a very strong elastic anisotropy. This elastic anisotropy is considered to be closely related to the excellent cold workability, low Young's modulus, high elastic deformability, high strength, etc. of the titanium alloy member according to the present invention.
<4> Thus, according to the titanium alloy member of the present invention, the average Young's modulus can be set to 70 GPa or less, 65 GPa or less, 60 GPa or less, or 55 GPa or less by appropriately selecting the composition, heat treatment, and the like. Further, the tensile elastic limit strength can be 750 MPa or more, 800 MPa or more, 850 MPa or more, 900 MPa or more, 1000 MPa or more, 1400 MPa or more, 1500 MPa, or even 2000 MPa or more.
(6) Applications The titanium alloy member of the present invention utilizes its excellent workability, low Young's modulus, high strength or anisotropy, etc., and further, in combination with its light weight and corrosion resistance, It can be applied to products in various forms.

  For example, it is effective as a product such as an automobile, a jewelry, a sports / recreation product, a medical device, a part of the product, a material (wire material, plate material, etc.) and the like. Specifically, it constitutes all or part of the following products, or is used as a material for such products.

For example, golf clubs (especially driver's face and shaft), bio-related products (artificial bones and joints, etc.), catheters, portable items (glasses, watches (watches), barrettes (hair ornaments), necklaces, bracelets, earrings , Earrings, rings, tie pins, brooches, cuff links, belts with buckles, lighters, fountain pens, key holders, keys, ballpoint pens, mechanical pencils, etc.), portable information terminals (cases for mobile phones, portable recorders, mobile personal computers, etc.), Coil springs for suspensions or engine valves, transmission belts (CVT hoops, etc.).
B. Examples Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples.
(Example)
Each sample according to this example described below was manufactured by using the manufacturing method of the present invention.
(1) Sintered material (Sample Nos. 1 to 10)
As raw materials, commercially available hydrogenated / dehydrogenated Ti powder (-# 325,-# 100), Nb powder (-# 325) which is a substitutional element, Ta powder (-# 325), V powder (-# 325) ), Hf powder (-# 325) and Zr powder (-# 325). Oxygen which is an interstitial element was prepared from the Ti powder containing O or the high oxygen Ti powder containing O by heat-treating the Ti powder in the atmosphere. However, since it is not easy to manage the amount of oxygen, unless the amount of oxygen is consciously adjusted, about 0.15 to 0.20 mass % of O can be mixed into the titanium alloy as an inevitable impurity. Incidentally, the high oxygen Ti powder can be obtained by heating the Ti powder in the atmosphere at 200 ° C. to 400 ° C. × 30 minutes to 128 hours.

  These raw material powders were appropriately selected, blended and mixed so as to satisfy the parameters Md and Bo, and mixed powders having various compositions corresponding to desired samples were prepared (powder preparation step). The specific composition of each sample will be described later. In addition, although the V-type mixer was used for mixing each raw material powder, you may use a ball mill, a vibration mill, a high energy ball mill, etc.

This mixed powder was subjected to CIP molding (cold isostatic pressing) at a pressure of 4 ton / cm 2 to obtain a molded body (molding step). The obtained molded body was sintered by heating at 1300 ° C. for 16 hours in a vacuum of 1 × 10 −5 torr to obtain a sintered body (titanium alloy ingot) (sintering step, member forming step).
<1> Cold swage member (Sample Nos. 1, 4 to 10)
A φ55 mm titanium alloy ingot produced by the above-described sintering process was hot worked to φ15 mm (hot working step). After processing it to φ4 mm with a cold swage (first cold working process), strain relief annealing was performed at 900 ° C. (annealing process). The φ4 mm material thus obtained was further subjected to cold swaging so as to obtain a desired cold working rate (second cold working step).

Hereinafter, the composition and the cold working rate will be described for each sample.
(A) Sample No. 1, 4
Sample No. 1 (Ti-30Nb-10Ta-5Zr-0.4O (0.4 mass % oxygen): the ratio is mass %, the same applies hereinafter), 4 (Ti-35Nb-2.5Ta-7.5Zr-0.4O) is obtained by further cold-working the material from φ4 mm to φ2 mm. The cold working rate of both samples is 75%.
(B) Sample No. 5
Sample No. 5 (Ti-35Nb-9Zr-0.4O) is obtained by further cold-working the material from φ4 mm to φ2.83 mm. The cold working rate of this sample is 50%.
(C) Sample No. 6-1 to 6-5
Sample No. different only in oxygen amount. 6-1 to 6-5 (Ti-12Nb-30Ta-7Zr-2V-xO: x is a variable), the material from φ4 mm to φ1.26 mm,
Further, it is cold worked. The cold working rate of each sample is 90%. The oxygen content of each sample is shown in Table 2.
(D) Sample No. 7-10
Sample No. 7 to 10 are different in composition, but are common in that the material is cold worked from φ4 mm to φ1.79 mm. The cold working rate of each sample is 80%.

The composition of each sample is as follows. 7 (Ti-28Nb-12Ta-2Zr-4Hf-0.8O), Sample No. 8 (Ti-17Nb-23Ta-8Hf-0.53O), Sample No. 9 (Ti-14Nb-29Ta-5Zr-2V-3Hf-1O), Sample No. 10 (Ti-30Nb-14.5Ta-3Hf-1.2O).
<2> Cold rolled member (Sample No. 2, 3)
Sample No. A titanium alloy ingot (thickness 4 mm) having the same composition as that of No. 1 is cold-rolled to obtain a 0.9 mm thick plate (Sample No. 2) and a 0.4 mm thick plate (Sample No. 3). (Cold working process). The respective cold working rates are 94% and 97.3%.

The cold working at this time was performed using a cold rolling mill without intermediate annealing. Specifically, Sample No. In the case of 2, a 0.5 mm pass was passed until the plate thickness became 0.9 mm. Sample No. In No. 3, the plate material is further processed while adjusting the path to a plate thickness of 0.4 mm.
(2) Melted lumber (Sample Nos. 11 and 12)
As a titanium raw material, commercially available granular sponge titanium (particle size of 3 mm or less) was used. Nb powder (-# 325), Ta powder (-# 325), V powder (-# 325) and Zr powder (-# 325) are mixed as a raw material for the substitutional alloy element, and this mixed powder is mixed with a pressure of 2 ton / A mold was formed at cm 2, and this was crushed into granules having a particle size of 3 mm or less. At this time, the composition of the substitutional alloy element was adjusted by blending the raw material powders and mixing them so as to satisfy the parameters Md and Bo described above according to the desired sample.

  Each granular raw material thus obtained was uniformly mixed at a predetermined ratio, melted by an induction skull method, held at 1800 ° C. for 20 minutes, and then formed into an ingot by die casting (member forming step, melting step or Melting and casting process).

  Here, it was decided that the substitutional alloy component raw material was produced from the powder compact because each of the melting points of the substitutional alloy elements was extremely high, and they were prone to segregation during melting and casting, which was attributed to them. This is to avoid as much as possible the deterioration of the quality of the titanium alloy member. Note that oxygen as an interstitial element was prepared with O contained in the sponge titanium.

  A φ55 mm × 200 mm die casting ingot produced by this melting process was hot-worked at 1000 ° C. to obtain φ15 mm (hot working step). After processing it to φ4 mm with a cold swage (first cold working process), strain relief annealing was performed at 900 ° C. (annealing process). The φ4 mm material thus obtained was further cold worked to φφ1 26 mm (second cold working step). In this case, the cold working rate is 90%.

In this way, sample No. which is a melting material is obtained. 11 and 12 were produced. Sample No. 11 and sample no. 12 is sample No. 1 above. 6 and the substitutional alloy component are the same, but only the oxygen amount is different (Ti-12Nb-30Ta-7Zr-2V-xO: x is a variable). The oxygen content of each sample is shown in Table 2.
(3) Aging material (Sample Nos. 13 and 14)
Sample No. The same specimen as that of No. 6-3 was further subjected to aging treatment, and sample No. 13 and 14 were produced.

  Sample No. 13 is sample No. After the second cold working step 6-3, an aging treatment is performed at 250 ° C. for 30 minutes (parameter P = 10.3).

Sample No. 14 is Sample No. After the second cold working step 6-3, an aging treatment of 400 ° C. × 24 hours (parameter P = 14.4) was performed.
(Comparative example)
As a comparative example, a cold swage material (trade name: DAT51) having a composition of Ti-22V-4Al ( mass %) was prepared. This titanium alloy round bar (φ150 mm) was machined to φ6 mm by hot working. Then, it was set as a comparative sample as a final wire having a diameter of 4 mm with a cold swage.
(Measurement)
(1) Crystal structure Sample No. A crystal structure of 1 to 12 using a rotating cathode type X-ray diffractometer, 40 kV, 70 m
The measurement was performed by the usual θ-2θ method under the conditions of A with CoKα rays and a monochromator. As a representative example, Sample No. The result in 2 is shown in FIG.

In each sample, three diffraction lines were confirmed, and as a result of diffraction, it was found that this crystal structure was a body-centered cubic crystal. However, strictly speaking, in the case of FIG. 2, there is a possibility of a body-centered tetragonal crystal, but it is difficult and not necessary to accurately distinguish between the two.
(2) Texture
<1> Sample No. For the textures of 1 to 12 and the comparative sample, pole figures were measured using the Schlutz reflection method described above. Table 1 shows the measurement conditions at this time.

However, in order to facilitate measurement, the form of each sample was adjusted as follows.
(A) Sample No. In Nos. 1 and 4 to 12, six wires cut to about 15 mm were arranged in the same direction with respect to the processing direction, embedded in resin, and polished to the maximum cross-sectional area to obtain samples for measurement.

  The diffraction angle of (110) diffraction reflection used at this time is 2θ = 44.9 ° (sample Nos. 1 and 4) or 2θ = 44.7 ° (sample No. 5). The folding angle is 2θ = 49.0 °.

  Sample No. at this time 1 (110) pole figure is shown in FIG. 4 (110) pole figure is shown in FIG. 5 (110) pole figures are shown in FIG.

In the figure, for example, “one scale 1000 cps” means that one interval between contour lines corresponds to 1000 cps of X-ray diffraction intensity (the same applies to the case of 500 cps). ).
(B) Sample No. 2 and Sample No. In No. 3, each plate material was cut into a disk shape of about φ26 mm by electric discharge machining and used as a measurement sample.

  The measurement conditions, the diffraction angle of (110) diffraction reflection, and the diffraction angle of the background portion are the same as those described above.

Sample No. at this time 2 (110) pole figure is shown in FIG. A (110) pole figure of 3 is shown in FIG.
(C) In the comparative sample, four wires cut in the processing direction were sample No. Similar to 1 and the like, it was embedded in a resin and polished to the maximum cross-sectional area to obtain a measurement sample.

  The diffraction angle of (110) diffraction reflection used at this time is 2θ = 46.2 °, and the diffraction angle of the background portion is 2θ = 49.0 °.

The (110) pole figure at this time is shown in FIG. 8A.
<2> Next, in order to objectively and quantitatively evaluate the distribution (degree of dispersion) of the measured value (X) obtained for each sample by this measurement, statistical processing is performed for each sample. A second moment (ν2) and a third moment (ν3) around the average value (Xm) were calculated. Their definitions are as described above.

  However, when performing statistical processing on these measurement values, it is necessary to assume that each measurement point is equivalent on the pole figure. In this embodiment, as shown in Table 1, α ′ and β are measured by moving them at an equal angle of 5 °, respectively. Therefore, the measurement points are not evenly distributed on the pole figure. Therefore, in order to correct this and make each measurement point equivalent, a weighting function W is introduced and W is multiplied instead of (1 / N) in each of the above-described equations. Of course, if the measurement points on the pole figure are evenly distributed, w is always a constant value, and W = w / (Nw) = 1 / N can be written, and the weighting function W becomes equal to 1 / N. .

  This weighting function W is defined by the following equation using the area w indicated on the pole figure by one measurement point (for example, wi, wj, wk) as shown in FIG. These equations are shown together.

Average value: Xm = ΣWX
Second moment around average value (Xm): ν2 = ΣW (X−Xm) 2
Third moment around average value (Xm): ν3 = ΣW (X−Xm) 3
Weight function: W = w / (Σw)
In order to facilitate comparison between different samples, the second moment (ν2) and the third moment (ν3) are expressed by the mean square (Xm2) and the mean cube (Xm3), respectively. The divided value was determined.

  The range of the sum (Σ) is ideally determined by the total area on the pole figure. In the case of a wire such as 1, it is very difficult to measure such a pole figure. Therefore, the measurement range shown in Table 1 was set as the total range (20 ° <α ′ <90 °, 0 ° <β <360 °).

The results thus obtained for each sample are shown in Table 2.
<3> Further, for each sample, the maximum value (maximum value) among the measurement values measured in the range of 55 ° <α ′ <65 ° and β along the machining direction is also shown in Table 2. Indicated. However, in Table 2, it displayed with the magnification based on the average value (Xm).
(3) Dislocation density, etc.
<1> Sample No. In order to perform TEM (transmission electron microscope) observation on No. 1, a thin film for observation was formed using an FIB (focused ion beam) apparatus or an ion milling apparatus.

  FIG. 10 shows a photograph (bright field image) obtained by observing the metal structure inside the crystal grains with a TEM. From the photograph shown in FIG. 10, no dislocation that can be clearly recognized as a line defect was observed. In addition, when the crystal grains were observed by a diffraction contrast method, no dislocations were clearly confirmed.

  Sample No. FIG. 11 shows a photograph (bright-field image) of the metallographic structure in the crystal grains observed by TEM for the sample (sample No. 1 ′) manufactured in the middle of processing in FIG. This sample No. 1 'is obtained by processing an ingot of 55 mm to 15 mm by hot swaging.

  In the photograph shown in FIG. 11, dislocations were observed in the metal structure. When the dislocation density at this time was estimated under the following conditions, it was about 1010 / cm2. Therefore, it can be considered that the dislocation density is at most 1011 / cm 2 or less.

Observation range: Vertical (3 μm) × Horizontal (4 μm) × Sample thickness (0.07 μm)
Total length of dislocation line: 3μm × 24
<2> The above-mentioned sample No. FIGS. 12 and 13 show metallographic photographs of dark field images obtained by observing 1 with a TEM. These two photographs are the same place observed, but are observed with a tilt angle of about 20 ° by tilting the sample.

In both cases, the electron diffraction pattern shows the (111) plane. However, in the dark field image using the 110 diffraction spots, it can be seen that the shining portion has moved about 200 nm. This suggests that the observed (111) plane is curved, and the radius of curvature was about 500 to 600 nm when calculated from both photographs.
<3> Similarly, when the dislocation density of the comparative sample as a comparative example was determined, it was 1015 / cm 2 or more.
(4) Other
<1> Energy level Md of d electron orbit and bond order Bo
For each sample, the composition average value of the energy level Md of the d electron orbital and the composition average value of the bond order Bo were calculated by the DV-Xα cluster method. The results are shown in Tables 2 and 3.
<2> Mechanical properties Mechanical properties such as average Young's modulus and tensile strength were determined for each sample. The results are shown in Tables 2 and 3.

These mechanical properties were obtained from a stress-strain diagram by measuring the relationship between load and elongation using an Instron testing machine. The Instron testing machine is a universal tensile testing machine manufactured by Instron (manufacturer), and the drive system is electric motor control.

(Evaluation and discussion)
(1) About pole figure Sample No. concerning the titanium alloy member of the present invention. When comparing the pole figures 1 to 5 (FIGS. 3 to 7) and the pole figure of the comparative sample (FIG. 8), the following can be understood.
<1> Sample No. For 1 to 5, it can be seen that the (110) plane is very strongly oriented in some directions. That is, it is estimated that the titanium alloy member has very strong elastic anisotropy.

  For example, when viewing FIG. 3, the deviation of the measurement value is very large with respect to the entire measurement surface, and the measurement value is very prominent at a certain portion. This protrusion indicates that the (110) plane or the (101) plane is concentrated in the vicinity of α ′ = 60 ° along the processing direction, that is, in a direction inclined by 30 ° from the normal direction of the sample.

  This strong orientation of the (110) plane or the (101) plane indicates the sample No. It can be interpreted as reflecting a strong elastic anisotropy of 1. As a result of cold working this material having strong elastic anisotropy, sample No. No. 1 is a titanium alloy member in which crystal planes with very high rigidity (high-rigidity crystal planes) are aligned along the cylindrical outer shape, flexible against bending deformation, and have high strength in the longitudinal direction. it is conceivable that.

  Sample No. 2 and sample no. Comparing the pole figure with FIG. 3 (FIGS. 6 and 7), it can be seen that the deviation of the measured value in the pole figure increases as the machining rate increases. In other words, the higher the processing rate, the higher the orientation of the high-rigidity crystal plane in a specific direction, as in the case described above, suggesting that the titanium alloy member according to the present invention is flexible and has high strength. It seems that it appears more strongly.

  And, such a titanium alloy member having strong elastic anisotropy has a high-rigidity crystal face, while having a low-rigidity crystal face that is easily deformed. It is considered that good workability can be obtained.

It should be noted that at this stage, these considerations are only speculations, and details are still unknown.
<2> On the other hand, when the pole figure of the comparative sample (FIG. 8) is observed, it can be seen that the measured values are relatively uneven, and the elastic anisotropy is considered to be smaller than that of the titanium alloy member of the present invention.
(2) ν2 / Xm2 and ν3 / Xm3
ν2 / Xm2 indicates that the larger the value, the greater the deviation of the measured value (X). In addition, ν3 / Xm3 indicates that the larger the positive number range, the more the measured value (X) is distributed in a portion protruding larger than the average value (Xm).
<1> Sample No. Looking at 1 to 12, both ν2 / Xm2 and ν3 / Xm3 show relatively large values. This is because the deviation of the measured value with respect to the entire measurement surface of the pole figure is large, indicating that the (110) crystal plane of the titanium alloy member of the present invention is strongly oriented in a specific direction. Thus, by using ν2 / Xm2 and ν3 / Xm3, the degree of texture orientation can be objectively and quantitatively evaluated.

Same as described for pole figure, but with sample no. 2 and sample no. 3 is compared with the titanium alloy member of the present invention, it can be seen that as the cold work rate increases, ν2 / Xm2 and ν3 / Xm3 increase, and the (110) crystal plane is strongly oriented in a specific direction.
<2> Looking at the comparative sample, ν3 / Xm3 is relatively small. This indicates that the protrusion of the measured value at a specific position is small. Compared to 1 etc., the degree of texture orientation seems to be small.
(3) About metallographic photographs
<1> The curvature of the (111) plane observed from the metallographic photographs shown in FIGS. 12 and 13 has already been mentioned, but a slightly curved crystal plane was also observed in high resolution observation.

From this, it can be considered that the titanium alloy member of the present invention is less influenced by processing due to the curvature of the crystal plane and improves (cold) workability without introducing dislocations.
<2> In the metal structure photograph shown in FIG. 11, dislocations were observed in a state where 110 diffraction spots were strongly excited, but were hardly observed when excitation at 110 diffraction spots was eliminated.

  This shows that the displacement component around the dislocation shown in FIG. 11 is remarkably biased in the <110> direction, which can be said to be a manifestation of very strong elastic anisotropy of the titanium alloy member. .

It is considered that such characteristics may be a source of the above-described curvature of the crystal plane and, in turn, processability such as rubber. However, details are not yet clear.
(4) Other
<1> Energy level Md of d electron orbital and bond order Bo
Sample No. In any of the titanium alloy members 1 to 14, Md and Bo are in the range of 2.43 <Md <2.49, 2.86 <Bo <2.90, and good cold workability and low Young It can be seen that the balance with the rate is achieved.
<2> Mechanical properties Sample No. As can be seen from a comparison between 1 and the like and a comparative sample, the titanium alloy member of the present invention has a remarkably low Young's modulus and a sufficiently high tensile strength. Sample No. As can be seen from 13, 14, etc., excellent tensile elastic limit strength and elastic elongation are exhibited. Therefore, the titanium alloy member of the present invention has a remarkable elastic deformability (about 2.5%). On the other hand, the elastic deformability of the titanium alloy of the comparative example is only about 1% at most, which is insufficient.
<3> Finally, workability between the titanium alloy member of the present invention and a conventional titanium alloy material will be examined.

  The conventional titanium alloy material (DAT51) has little deterioration in drawability even after cold working, and when the cold working rate becomes 10 to 15%, a rapid decrease in elongation occurs. This seems to be caused by an increase in dislocation density (dislocation density of 1015 / cm 2 or more).

  On the other hand, in the titanium alloy member of the present invention, even if the cold work rate was 99% or more, there was no sudden decrease in elongation and the cold workability was very good.

As described above, the titanium alloy member of the present invention has characteristics that are excellent in workability, flexible and high strength, which cannot be obtained with conventional materials. By using each of these properties alone or synergistically, the use can be expanded immeasurable.

The scope of the claims

1. 40% by mass or more of titanium (Ti), a total of 90% by mass or more of the titanium and other IVa group elements and Va group elements, oxygen (O), nitrogen (N) and carbon (C And a total of one or more elements in the interstitial element group consisting of 0.25 to 2.0 mass% ,
a ratio of the interatomic distance on the c axis to the interatomic distance on the a axis (c / a) is a body-centered tetragonal or body-centered cubic crystal grain having a ratio of 0.9 to 1.1,
The pole figure of the (110) or (101) crystal plane of the crystal grain is parallel to the plane including the machining direction in the range of 20 ° <α ′ <90 ° and 0 ° <β <360 ° by the Schlutz reflection method. When the measured values (X) that are measured and evenly distributed on the pole figure are statistically processed, the second moment (ν2) around the average value (Xm) defined by the following equation is the square of the average value (Xm2 ) (Ν2 / Xm2) divided by 0.3 or more, and a value obtained by dividing the third moment (ν3) around the average value (Xm) defined by the following equation by the cube of the average value (Xm3) (ν3 / Xm3) is 0.3 or more, and 1.6 times the average value (1.6Xm) or more in the measurement value measured in the range of 55 ° <α ′ <65 ° and β along the machining direction A titanium alloy member characterized by having a texture containing the measured values of
Second moment: ν2 = {Σ (X−Xm) 2} / N
Third moment: ν3 = {Σ (X−Xm) 3} / N
(However, N is the number of samplings.)

2 . Wherein one or more elements in the interstitial element group, the titanium alloy of the range first claim of claim total is 0.6 to 1.5 mass%.

3 . The compositional average value of the substitutional element is 2.43 <Md <2.49 for the energy level Md of the d-electron orbital, which is a parameter obtained by the DV-Xα cluster method, and the compositional average value of the substitutional element is 2.2. A preparation step of preparing a raw material composed of titanium and an alloy element having a specific composition of 86 <Bo <2.90;
A member forming step of forming a titanium alloy member made of the raw material after the preparation step;
The manufacturing method of the titanium alloy member characterized by the above-mentioned.

4 . The preparation step is a powder preparation step of preparing a raw material powder having the specific composition,
The method for producing a titanium alloy member according to claim 3 , wherein the member forming step is a sintering step for producing a sintered material from the raw material powder after the powder preparation step.

5 . The method for producing a titanium alloy member according to claim 3 , wherein the member forming step is a smelting step of manufacturing a smelting material from the raw material after the preparation step.

6 . Furthermore, the manufacturing method of the titanium alloy member of Claim 4 or 5 provided with the cold working process of cold-working the said sintered material or melted material.

7 . The cold working step is a step of setting the cold working rate to 10% or more,
After the cold working step, a Larson-Miller parameter P (hereinafter, simply referred to as “parameter P”) defined by the following formula within a processing temperature range of 150 ° C. to 600 ° C. is 8. The method for producing a titanium alloy member according to claim 6, further comprising an aging treatment step of performing an aging treatment of 0.0 to 18.5.
P = (T + 273) · log10t) / 1000
(However, T is a processing temperature (° C.) and t is a processing time (hour).)

8 . The aging treatment step is a step in which the parameter P is 8.0 to 12.0 when the treatment temperature is in the range of 150 ° C to 300 ° C.
The titanium alloy member according to claim 7, wherein the titanium alloy member obtained after the aging treatment step has a tensile elastic limit strength of 1000 MPa or more, an elastic deformability of 2.0% or more, and an average Young's modulus of 75 GPa or less. Method.

9 . The aging treatment step is a step in which the parameter P is 12.0 to 14.5 when the treatment temperature is in the range of 300 ° C to 600 ° C.
The titanium alloy member according to claim 7, wherein the titanium alloy member obtained after the aging treatment step has a tensile elastic limit strength of 1400 MPa or more, an elastic deformability of 1.6% or more, and an average Young's modulus of 95 GPa or less. Method.

10 . A titanium alloy member characterized by having a dislocation density inside a crystal grain of 1011 / cm2 or less when cold-worked by 50% or more.

11 . 40 mass% or more of titanium, IVa group elements other than the titanium and Va group elements other than the titanium including the titanium of 90 mass% or more, oxygen totaling 0.25 to 2.0 mass%, The titanium alloy member according to claim 10 , comprising at least one element in an interstitial element group consisting of nitrogen and carbon.

12 . The compositional average value of the substitutional element is 2.43 <Md <2.49 with respect to the energy level Md of the d electron orbital, which is a parameter obtained by the DV-Xα cluster method, and the compositional average value of the substitutional element with respect to the bond order Bo is 2. A titanium alloy member comprising titanium and an alloy element having a specific composition of 86 <Bo <2.90.

13 . The titanium alloy member according to claim 12, wherein the dislocation density inside the crystal grains is 1011 / cm2 or less when cold working of 50% or more is performed.

wrap up

40% by weight or more of titanium (Ti) and IVa group elements and / or Va group elements other than titanium, the total including which is 90% by weight or more, and 0.25 to 2.0% by weight in total The ratio of the interatomic distance on the c-axis to the interatomic distance on the a-axis (c / a) is 0, including one or more elements in an interstitial element group consisting of oxygen, nitrogen, and carbon A titanium alloy member characterized by having a body-centered tetragonal or body-centered cubic crystal having a basic structure of 9 to 1.1.
This titanium alloy member has workability not found in conventional titanium alloys, is flexible and has high strength, and can be used for various products.

Claims (12)

40% by mass or more of titanium (Ti), a total of 90% by mass or more of the titanium and other IVa group elements and Va group elements, oxygen (O), nitrogen (N) and carbon (C ) and one or more elements in the interstitial element group consisting of a total and a 0.6 to 2.0 wt%,
a ratio of the interatomic distance on the c axis to the interatomic distance on the a axis (c / a) is a body-centered tetragonal or body-centered cubic crystal grain having a ratio of 0.9 to 1.1,
The pole figure of the (110) or (101) crystal plane of the crystal grain is parallel to the plane including the machining direction in the range of 20 ° <α ′ <90 ° and 0 ° <β <360 ° by the Schlutz reflection method. When the measured values (X) that are measured and evenly distributed on the pole figure are statistically processed, the second moment (ν2) around the average value (Xm) defined by the following equation is the square of the average value (Xm ² ) divided by (ν2 / Xm ² ) is 0.3 or more, and the third moment (ν3) around the mean value (Xm) defined by the following equation is divided by the cube of the mean value (Xm ³ ) The value (ν3 / Xm ³ ) is 0.3 or more, and 1.6 times the average value (1 in the measurement values measured in the range of 55 ° <α ′ <65 ° and β along the machining direction (1 .6Xm) a titanium alloy member characterized by having a texture including a measured value of not less than 6.Xm).
Second moment: ν2 = {Σ (X−Xm) ² } / N
Third moment: ν3 = {Σ (X−Xm) ³ } / N
(However, N is the number of samplings.) The titanium alloy member according to claim 1, wherein the one or more elements in the interstitial element group are 0.6 to 1.5 mass% in total. 2. The method for producing a titanium alloy member according to claim 1, wherein the compositional average value of the substitutional element is 2.43 <Md <2. With respect to the energy level Md of the d electron orbit, which is a parameter obtained by the DV-Xα cluster method. A preparation step of preparing a raw material composed of titanium and an alloy element having a specific composition in which the compositional average value of the substitutional element with respect to the bond order Bo is 2.86 <Bo <2.90;
A member forming step of forming a titanium alloy member made of the raw material after the preparation step;
A cold working step of cold working the titanium alloy member after the member forming step;
The manufacturing method of the titanium alloy member characterized by the above-mentioned . The method for manufacturing a titanium alloy member according to claim 3, wherein the member forming step is a smelting step of manufacturing a smelting material from the raw material after the preparation step. The compositional average value of the substitutional element is 2.43 <Md <2.49 for the energy level Md of the d-electron orbital, which is a parameter obtained by the DV-Xα cluster method, and the compositional average value of the substitutional element is 2.2. A preparation step of preparing a raw material composed of titanium and an alloy element having a specific composition of 86 <Bo <2.90;
A member forming step of forming a titanium alloy member made of the raw material after the preparation step;
With
The preparation step is a powder preparation step of preparing a raw material powder having the specific composition,
The method for producing a titanium alloy member, wherein the member forming step is a sintering step for producing a sintered material from the raw material powder after the powder preparation step. Furthermore, the manufacturing method of the titanium alloy member of Claim 5 provided with the cold working process of cold-working the said sintered material . The cold working step is a step of setting the cold working rate to 10% or more,
After the cold working step, a Larson-Miller parameter P (hereinafter, simply referred to as “parameter P”) defined by the following formula within a processing temperature range of 150 ° C. to 600 ° C. is 8. The manufacturing method of the titanium alloy member of Claim 3 or 6 provided with the aging treatment process which performs the aging treatment used as 0.0-18.5.
P = (T + 273) · (20 + log ₁₀ t) / 1000
(However, T is a processing temperature (° C.) and t is a processing time (hour).) The aging treatment step is a step in which the parameter P is 8.0 to 12.0 when the treatment temperature is in the range of 150 ° C to 300 ° C.
The method for producing a titanium alloy member according to claim 7, wherein the titanium alloy member obtained after the aging treatment step has a tensile elastic limit strength of 1000 MPa or more, an elastic deformability of 2.0% or more, and an average Young's modulus of 75 GPa or less. The aging treatment step is a step in which the parameter P is 12.0 to 14.5 when the treatment temperature is in the range of 300 ° C to 600 ° C.
The method for producing a titanium alloy member according to claim 7, wherein the titanium alloy member obtained after the aging treatment step has a tensile elastic limit strength of 1400 MPa or more, an elastic deformability of 1.6% or more, and an average Young's modulus of 95 GPa or less. 40% by mass or more of titanium, IVa group element other than titanium and Va group element other than the titanium including 90% by mass in total, and 0.6 to 2.0% by mass of oxygen, It contains one or more elements in an interstitial element group consisting of nitrogen and carbon, and the dislocation density inside the crystal grains is 10 ¹¹ / cm ² or less when cold-worked by 50% or more. A characteristic titanium alloy member. The compositional average value of the substitutional element is 2.43 <Md <2.49 for the energy level Md of the d-electron orbital, which is a parameter obtained by the DV-Xα cluster method, and the compositional average value of the substitutional element is 2.2. The titanium alloy member according to claim 10 , comprising titanium and an alloy element having a specific composition satisfying 86 <Bo <2.90. The titanium alloy member according to claim 11, wherein the dislocation density inside the crystal grains is 10 ¹¹ / cm ² or less when cold working of 50% or more is performed.

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